1. CHS MEKANIKAFLUIDA (S1 Reguler) CHS220803E MEKANIKAFLUIDA (S1 Ekstensi) Departemen Teknik Kimia FT-UI Pengajar : Ir. SUKIRNO M.Eng/Ir. Diyan S M.Eng

2. Periode 2009-2010 Lectures : Senin 19:00-21:30 K-204
Selasa 10:00-12:30 K-106
Kamis 10:00-12:30 K-210
Sbl Mid Test Pak Sukirno
Stl Mid Test Pak Diyan S
Tutorials : Asisten

3. Assessment Pak Kirno 50% 25% : MidTest (2 jam)
10% : Kuis selama kelas/tutorial
15% : Tugas

4. Books Noel de Nevers Fluid Mechanics for Chemical Engineer, Second Ed.
Coulson & Richardson Chemical Engineering, Vol 1, 5e (1996) Butterworth-Heinemann

5. ALIRAN GAS KECEPATAN TINGGI, SATU DIMENSI INTERAKSI FLUIDA DAN PADATAN
GARIS BESAR KULIAH
PENDAHULUAN
Mengenal aplikasi Mekanika Fluida, Fluida dan propertiesnya
FLUIDA STATIK
Pressure, Pascal’s Principle,Gravity and fluid pressure, Measurement of pressure, Archimedes’ Principle
FLUIDA MENGALIR (FLUID FLOW)
Persamaan dasar: Pers. Kontinuitas (Neraca massa) Pers. Bernoulli (Neraca Energi) dan aplikasiBernoulli pada flowmeter (orificemeter, venturimeter), alat transfer fluida (pompa)
KEHILANGAN FRIKSI (FRICTION LOSS) DALAM PIPA
Faktor friksi, diagram Moody, Perhitungan friksi pada pipa sudden contraction/expansion fitting,
APLIKASI NERACA MOMENTUM UNTUK PERHITUNGAN GAYA PADA PIPA
Neraca momentum, perhitungan gaya pada belokan
ALIRAN GAS KECEPATAN TINGGI, SATU DIMENSI
Kecepatan suara, Aliran stedi fritionless, nozzle choking, aliran dengan friksi dan pemanasan, nozzle-difusser
INTERAKSI FLUIDA DAN PADATAN
Lapisan batas dan Gaya seret (drag force), Friksi fluida dalam media berpori, Pers. Blake-Kozeny, Ergun Darcy, Fluidisasi, Filtrasi,
Internal and external flows
Air, sea-water – oil & gas – fresh water, mud, hydraulic oil
Drilling, pumping, extraction, power generation, effluent disposal, fire systems, sanitation

6. Fluid Mechanics Definition Engineering applications
The study of liquids and gasses at rest (statics) and in motion (dynamics)
Engineering applications
Oil /process fluid in pipelines
Pumps, filters, rivers, etc
Groundwater movement
Blood in capillaries

7. Industrial application …
Home : water, heating, appliances – fridge, washing / dish-washer machines
Car: engine cooling + car heater, fuel, oil, hydraulics, external aerodynamics
Aeroplane: fuel, hydraulics, air-conditioning, cabin pressurization, oxygen, sanitation, external aerodynamics, gas turbines

8. DIAGRAM SISTIM ALIRAN FLUIDA
Storage
Pipe system
Valves
Flow Measurement
Pump
Process/Resistance

9. SUBDIVISI MEKANIKA FLUIDA
HYDRAULICS : the flow of water in rivers, pipes, canals, pump, turbines
HYDROLOGY : the flow of water in the ground
RESERVOIR MECHANICS : the flow of oil, gas and water in petroleum reservoir
AERODYNAMICS : the flow of air around aeroplanes, rocket projectils
METEOROLOGY : the flow of the atmosfeer
PARTICLE DYNAMICS : the flow of fluid around particles (dust settling, slurry, pneumatic transfort, fluidized be, air pollutant particles)
MULTIPLEPHASE FLOW oil well, carburetirs, fuel injector, combustion chamber, sprays.
COMBINATION OF FLUID FLOW with chemical reaction in combustion chamber, with mass transfer di distillation or drying
VISCOUS DOMINATED FLOW; lubrication, injection molding, wire coating, volcanoes, continental drift

10. MENGENAL SIFAT FLUIDA Fluid Properties

11. What is a Fluid?
… a substance which deforms continuously under the action of shearing forces however small.
… unable to retain any unsupported shape; it takes up the shape of any enclosing container.
... we assume it behaves as a continuum

12. Liquids and gasses – What’s the difference?
Expands
Liquid
Free Surface
Liquids: Close packed, strong cohesive forces, retains volume, has free surface
Gasses: Widely spaced, weak cohesive forces, free to expand
Almost incompressible
Relatively easy to compress

13. Common Fluids Liquids: Gasses: Borderline:
water, oil, mercury, gasoline, alcohol
Gasses:
air, helium, hydrogen, steam
Borderline:
jelly, asphalt, lead, toothpaste, paint, pitch

14. Density
The density of a fluid is defined as its mass per unit volume. It is denoted by the Greek symbol, . kg
 water= 998 kgm-3 m
 = V
air =1.2kgm-3
kgm-3 m3
If the density is constant (most liquids), the flow is incompressible.
If the density varies significantly (eg some gas flows), the flow is compressible.
(Although gases are easy to compress, the flow may be treated as incompressible if there are no large pressure fluctuations)

15. Density Mass per unit volume (e.g., @ 20 oC, 1 atm)
Water rwater = 1000 kg/m3
Mercury rHg = 13,500 kg/m3
Air rair = 1.22 kg/m3
Densities of gasses increase with pressure
Densities of liquids are nearly constant (incompressible) for constant temperature
Specific volume = 1/density
950
960
970
980
990
1000 50
100
Temperature (C)
Density (kg/m3)

16. Specific Weight Weight per unit volume (e.g., @ 20 oC, 1 atm)
gwater = (998 kg/m3)(9.807 m2/s)
= 9790 N/m3
[= 62.4 lbf/ft3]
gair = (1.205 kg/m3)(9.807 m2/s)
= 11.8 N/m3
[= lbf/ft3]

17. Specific Gravity Ratio of fluid density to density at STP
20 oC, 1 atm)
Water SGwater = 1
Mercury SGHg = 13.6
Air SGair = 1

18. States of Matter
“a fluid, such as water or air, deforms continuously when acted on by shearing stresses of any magnitude.” - Munson, Young, Okiishi
Solid
Shear Stress t
Fluid

19. Fluid Deformation between Parallel Plates
Side view
Force F causes the top plate to have velocity U.
Distance between plates (b)
What other parameters control how much force is required to get a desired velocity?
Area of plates (A)
Viscosity!

20. Tangential force per unit area Rate of deformation
Shear Stress F v b
Tangential force per unit area
Rate of deformation
change in velocity with repect to distance
rate of shear

21. Dynamic and Kinematic Viscosity
Area A
Friction force F vb b v z
Absolute Viscosity
Kinematic Viscosity
Shear stess
(dyne/cm2 )
Shear strain rate
(s-1)
Dyne-s/cm2=Poise
N-s/m2=103 cP

22. Fluid classification by response to shear stress

23. Fluid Viscosity Examples of highly viscous fluids
______________________
Fundamental mechanisms
Gases - transfer of molecular momentum
Viscosity __________ as temperature increases.
Viscosity __________ as pressure increases.
Liquids - cohesion and momentum transfer
Viscosity decreases as temperature increases.
Relatively independent of pressure (incompressible)
molasses, tar, 20w-50 oil
increases
increases
_______

24. Role of Viscosity Statics Flows zero
Fluids at rest have no relative motion between layers of fluid and thus du/dy = 0
Therefore the shear stress is _____ and is independent of the fluid viscosity
Flows
Fluid viscosity is very important when the fluid is moving
zero

25. Perfect Gas Law
Note deviation from the text!
PV = nRT
R is the universal gas constant
T is in Kelvin
Use absolute pressure for P and absolute temperature for T

26. Bulk Modulus of Elasticity
Relates the change in volume to a change in pressure
changes in density at high pressure
pressure waves
_________
______ __________
2.00
2.05
2.10
2.15
2.20
2.25
2.30
2.35 20 40 60 80
100
Temperature (C)
Bulk Modulus of elasticity (GPa)
sound
Water
water hammer
speed of sound

27. Vapor Pressure 101 kPa liquid
1000
2000
3000
4000
5000
6000
7000
8000 10 20 30 40
Temperature (C)
Vapor pressure (Pa)
liquid
What is vapor pressure of water at 100°C?
101 kPa
Connection forward to cavitation!

28. Surface Tension Pressure increase in a spherical droplet DppR2 2pRs
0.050
0.055
0.060
0.065
0.070
0.075
0.080 20 40 60 80
100
Temperature (C)
Surface tension (N/m)
Pressure increase in a spherical droplet
DppR2
2pRs
Surface molecules
DppR2 = 2pRs

29. Example: Surface Tension
Estimate the difference in pressure (in Pa) between the inside and outside of a bubble of air in 20ºC water. The air bubble is 0.3 mm in diameter.
s = N/m
R = 0.15 x 10-3 m
Statics!
What is the difference between pressure in a water droplet and in an air bubble?

30. Bagaimana mengukur viskositas ?

31. GLASS CAPILLARY VISCOMETERS
ASTM D445
P = Pressure difference across capiller
R = Radius of capiller
L = Length od capiller
V = Volume fluida
 = Viscosity

32. A CALIBRATED HOLE IN THE BOTTOM.
(Poiseuille Eq.) 1 V x z
cP = fluid density X cSt 2

33. ROTARY VISCOMETER

34. Example: Measure the viscosity of water
Outer cylinder
Thin layer of water
Inner cylinder
The inner cylinder is 10 cm in diameter and rotates at 10 rpm. The fluid layer is 2 mm thick and 10 cm high. The power required to turn the inner cylinder is 50x10-6 watts. What is the dynamic viscosity of the fluid?

35. Solution Scheme Restate the goal
Identify the given parameters and represent the parameters using symbols
Outline your solution including the equations describing the physical constraints and any simplifying assumptions
Solve for the unknown symbolically
Substitute numerical values with units and do the arithmetic
Check your units!
Check the reasonableness of your answer
olution

36. Outline the solution Restate the goal
Identify the given parameters and represent the parameters using symbols
Outline your solution including the equations describing the physical constraints and any simplifying assumptions

37. Viscosity Measurement: Solution
Outer cylinder
Thin layer of water
Inner cylinder wr
2prh
Fwr
r = 5 cm
t = 2 mm
h = 10 cm
P = 50 x 10-6 W
10 rpm

38. APPROXIMATE PHYSICAL PROPERTIES OF COMMON LIQUIDS AT ATMOSPHERIC PRESSURE

39. Dimensions & Units
Tujuan : mereview satuan untuk menghilangkan kebingunan konversi satuan SI dan Engineering

40. Dimensions and Units
The dimensions have to be the same for each term in an equation
Dimensions of mechanics are
length
time
mass
force
temperature L T M
MLT-2 

41. Dimensions and Units Quantity Symbol Dimensions
Density r ML-3
Specific Weight g ML-2T-2
Dynamic viscosity m ML-1T-1
Kinematic viscosity  L2T-1
Surface tension  MT-2
Bulk mod of elasticity E ML-1T-2
These are _______ properties!
fluid 4
How many independent properties? _____

42. Units Unit: Particular dimension kg, m, s, oK (Systeme International)
slug, ft, s, oR (British Gravitational)
lbm, ft, s, oR (something else)

43. What’s a SLUG?! Unit of mass in the BG system (~ 14.59 kg, ~32.17 lbm)
1 lbf will accelerate a slug 1ft/s2
32.17 lb/14.59 kg = 2.2 lbm/kg

44. Secondary Units Force N = kg-m/s2 (Newton)
lbf = slug-ft/s2 (pound force)
= 32.2 lbm-ft/s2
Work (Force through a distance)
J = N-m (Joule)
ft-lbf (foot pound)
Energy (Work per time)
W = J/s (Watt)
ft-lbf/s (foot pound per sec)
hp 550 ft-lb/s (horsepower)

45. gc YANG SERING MEMBINGUNGKAN,
Fisika
Engineering
W = mg
W = mg /gc.
(g: gravitational acceleration).

46. Conversion of Units

47. MEKANIKA FLUIDA Tujuan Pengajaran
Memahami fenomena/konsepnya dan mampu mengaplikasikan PERSAMAAN DASAR fluida statik maupun fluida mengalir, untuk mendapatkan solusi persoalan praktis, yang sering dijumpai dalam enjinering terutama yang berkaitan dengan operasi teknik kimia seperti transportasi fluida, pengontakkan fluida-padatan, pemisahan fluida padatan.
PERSAMAAN DASAR MEKANIKA FLUIDA
H. Newton F= m.a
H. Kekekalan Massa
H. Kekekalan Energi (H.Termodinamika 1)
H. Termodinamika 2